150 



BIOLOGY OF THE PROTOZOA 



microns to great waving sheets of protoplasm almost as long as the 

 entire cell (Fig. 77). They are nsnally found in the peristomial area 

 inside the rows of membranelles or adoral zone and are named pre- 

 oral, endoral, paroral, etc., according to their positions in relation to 

 the mouth (Fig. 78). They are also frequently found in the gullet, 

 a single one, for example, in Paramecium, two in Glancoma, etc., 

 and are used exclusively for food-getting (see Maier, 1903), Schu- 

 berg, 1905, etc.). 



Fig. 78. — Diagram of a hypotrichous ciliate. az, adoral zone of membranelles; 

 c, anal and ventral cirri; e m, endoral membrane; e o, endoral cilia; p m, paroral mem- 

 brane; p c, preoral cilia; p o c, paroral cilia. (From Calkins.) 



Cirri.— Cirri are the most highly specialized of all the motile 

 organs of ciliates, the most characteristic forms occurring in the 

 Hypotrichida. They are placed more or less definitely on the 

 ventral surface, a group, variable in number, at the anterior end 

 being known as the frontal cirri, a similar group, also variable in 

 number, near the posterior end being known as the anal cirri, 

 while other groups may form caudal cirri, ventral cirri, marginal 

 cirri, etc. (Figs. 78, 79). 



Cirri are always broader at the base and taper gracefully to a 

 fine point. In cross-section near the base they are either circular. 



